Method for signaling control information, and apparatus therefor

ABSTRACT

A method is provided for transmitting a power headroom report at a user equipment (UE) in a wireless communication system. The UE configures a first cell group having a primary cell (PCell) and a second cell group having one or more secondary cells (SCells). The UE transmits the power headroom report. If the first cell group and the second cell group are managed by a same base station, the power headroom report indicates power headroom information regarding the first and second cell groups. If the first cell group and the second cell group are managed by different base stations, the power headroom report indicates power headroom information regarding only one of the first cell group and the second cell group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/192,667 filed on Jun. 24, 2016 (now U.S. Pat. No. 9,629,148 issued onApr. 18, 2017), which is a Continuation of U.S. patent application Ser.No. 14/416,940 filed on Jan. 23, 2015 (now U.S. Pat. No. 9,402,253issued on Jul. 26, 2016), which was filed as the National Phase ofPCT/KR2013/006958 on Aug. 1, 2013, which claims the benefit under 35U.S.C. §119(e) to U.S. Provisional Application Nos. 61/822,310 filed onMay 11, 2013, 61/807,785 filed on Apr. 3, 2013, 61/750,306 filed on Jan.8, 2013 and 61/678,600 filed on Aug. 1, 2012, all of which are herebyexpressly incorporated by reference into the present application.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless communication system and,more particularly, to a method for signaling control information and anapparatus therefor.

Wireless communication systems have been diversified in order to providevarious types of communication services such as voice or data service.In general, a wireless communication system is a multiple access systemcapable of sharing available system resources (bandwidth, transmit poweror the like) so as to support communication with multiple users.Examples of the multiple access system include a Code Division MultipleAccess (CDMA) system, a Frequency Division Multiple Access (FDMA)system, a Time Division Multiple Access (TDMA) system, an OrthogonalFrequency Division Multiple Access (OFDMA) system, a Single CarrierFrequency Division Multiple Access (SC-FDMA) system, and the like.

SUMMARY OF THE INVENTION

An object of the present invention devised to solve the problem lies ina method for efficiently transmitting and receiving control informationin a wireless communication system and an apparatus therefor. Morespecifically, an object of the present invention is to provide a methodfor efficiently transmitting and receiving control informationinter-site carrier aggregation (CA).

The technical problems solved by the present invention are not limitedto the above technical problems and other technical problems which arenot described herein will become apparent to those skilled in the artfrom the following description.

The object of the present invention can be achieved by providing amethod for transmitting and receiving at least one of controlinformation and a response signal at a user equipment (UE) in a carrieraggregation based wireless communication system including configuring afirst cell group having a primary cell (PCell), configuring a secondcell group having one or more secondary cells (SCells), performing aprocedure of transmitting and receiving at least one of specificcell-related control information and a response signal, wherein, if thefirst cell group and the second cell group are managed by the same basestation, at least one of the control information and the response signalis transmitted and received on the first cell group or the second cellgroup, and wherein, if the first cell group and the second cell groupare managed by different base stations, at least one of the controlinformation and the response signal is transmitted and received only onone of the first cell group or the second cell group according tocontrol information type.

In another aspect of the present invention, provided herein is a userequipment (UE) configured to transmit and receive at least one ofcontrol information and a response signal in a carrier aggregation basedwireless communication system including a radio frequency (RF) unit anda processor, wherein the processor is configured to configure a firstcell group having a primary cell (PCell), to configure a second cellgroup having one or more secondary cells (SCells) and to perform aprocedure of transmitting and receiving at least one of specificcell-related control information and a response signal, wherein, if thefirst cell group and the second cell group are managed by the same basestation, at least one of the control information and the response signalis transmitted and received on the first cell group or the second cellgroup, and wherein, if the first cell group and the second cell groupare managed by different base stations, at least one of the controlinformation and the response signal is transmitted and received only onone of the first cell group or the second cell group according tocontrol information type.

The first cell group and the second cell group may be managed bydifferent base stations and the control information may include at leastone of radio resource control (RRC) configuration/reconfigurationrelated information, radio link monitoring (RLM) related information,radio resource management (RRM) related information and handover relatedinformation.

At least one of the control information and the response signal may betransmitted and received only on the first cell group.

If the first cell group and the second cell group are managed bydifferent base stations and the control information includes at leastone of an SCell activation/deactivation message, a timing advancecommand (TAC), downlink control information (DCI) and aperiodic channelstate information (CSI), at least one of the control information and theresponse signal may be transmitted and received on a cell group, towhich the specific cell belongs.

If the control information includes a timing advance command (TAC) andthe first cell group and the second cell group are managed by the samebase station, the TAC may include a per-timing advance group (TAG) TACfor at least one of the first cell group and the second cell group, and,if the control information includes the TAC and the first cell group andthe second cell group are managed by different base stations, the TACmay include only a per-TAG TAC for a cell group, to which the specificcell belongs.

If the control information includes downlink control information (DCI)and the first cell group and the second cell group are managed by thesame base station, the DCI may include scheduling information of atleast one of the first cell group and the second cell group, and, if thecontrol information includes the DCI and the first cell group and thesecond cell group are managed by different base stations, the DCI mayinclude only scheduling information of a cell group, to which thespecific cell belongs.

According to the present invention, it is possible to efficientlytransmit/receive control information in a wireless communication system.More specifically, it is possible to efficiently transmit/receivecontrol information in inter-site carrier aggregation (CA).

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an evolved universalmobile telecommunication system (E-UMTS).

FIG. 2 is a diagram showing the structure of an evolved universalterrestrial radio access network (E-UTRAN) and a gateway.

FIGS. 3A and 3B are diagrams showing a user/control plane protocol.

FIG. 4 is a diagram showing the structure of a radio frame.

FIG. 5 is a diagram showing the structure of an uplink subframe.

FIG. 6 is a diagram showing a slot level structure of physical uplinkcontrol channel (PUCCH) format 1a/1b.

FIG. 7 is a diagram showing a slot level structure of PUCCH format2/2a/2b.

FIG. 8 is a diagram showing a random access procedure.

FIG. 9 is a diagram showing an uplink-downlink timing relationship.

FIG. 10 is a diagram showing a handover procedure.

FIG. 11 is a diagram showing an example of determining a PUCCH resourcefor acknowledgement/negative acknowledgement (ACK/NACK) transmission.

FIG. 12 is an ACK/NACK transmission procedure in a single cellsituation.

FIG. 13 is a diagram showing a carrier aggregation (CA) communicationsystem.

FIG. 14 is a diagram showing scheduling when a plurality of carriers isaggregated.

FIG. 15 is a diagram showing an example of allocating a PDCCH to a dataregion of a subframe.

FIG. 16 is a diagram showing a medium access control protocol data unit(MAC PDU).

FIG. 17 is a diagram showing an SCell activation/deactivation MACcontrol element (CE).

FIG. 18 is a diagram showing a timing advance command (TAC) MAC CE.

FIG. 19 is a diagram showing a power headroom report (PHR) MAC CE.

FIG. 20 is a diagram showing inter-site carrier aggregation (CA).

FIG. 21 is a diagram showing a signaling method/path according to oneembodiment of the present invention.

FIG. 22 is a diagram showing a base station (BS) and a user equipment(UE) to which the present invention is applicable.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following technologies can be applied to a variety of radio accesssystems, for example, CDMA (Code Division Multiple Access), FDMA(Frequency Division Multiple Access), TDMA (Time Division MultipleAccess), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA(Single Carrier Frequency Division Multiple Access), and the like. CDMAmay be embodied with wireless (or radio) technology such as UTRA(Universal Terrestrial Radio Access) or CDMA2000. TDMA may be embodiedwith wireless (or radio) technology such as GSM (Global System forMobile communications)/GPRS (General Packet Radio Service)/EDGE(Enhanced Data Rates for GSM Evolution). OFDMA may be embodied withwireless technology such as Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, andE-UTRA (Evolved UTRA). UTRA is a part of the UMTS (Universal MobileTelecommunications System). 3GPP (3rd Generation Partnership Project)LTE (long term evolution) is a part of the E-UMTS (Evolved UMTS), whichuses E-UTRA. 3GPP LTE employs OFDMA in downlink and employs SC-FDMA inuplink. LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE.

Although the following embodiments focus on the 3GPP LTE/LTE-A systemfor clarity of description, the technical features of the presentinvention are not limited thereto. It should be noted that specificterms disclosed in the present invention are proposed for theconvenience of description and better understanding of the presentinvention, and the use of these specific terms may be changed to anotherformat within the technical scope or spirit of the present invention.

First, the terms used in the present specification will be described.

FIG. 1 is a diagram showing a network structure of an E-UMTS. The E-UMTSis also called a Long Term Evolution (LTE) system. Communicationnetworks are widely arranged to provide a variety of communicationservices such as voice and packet data.

Referring to FIG. 1, an E-UMTS network mainly includes an EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN), an Evolved PacketCore (EPC) and one or more user equipments (UEs). The E-UTRAN includesone or more base stations (eNBs) 20 and one or more UEs 10 may belocated in one cell. A mobility management entity/system architectureevolution (MME/SAE) gateway 30 is located at an end of a network and isconnected to an external network. Downlink refers to communication fromthe eNB 20 to the UE 10 and uplink refers to communication from the UEto the eNB.

The UE 10 is a communication device held by a user and is also referredto as a mobile station (MS), a user terminal (UT), a subscriber station(SS) or a wireless device. The eNB 20 is generally a fixed stationcommunicating with the UE 10 and is also referred to as an access point(AP). The eNB 20 provides an endpoint of a user plane and a controlplane to the UE 10. One eNB 20 may be located in each cell. An interfacefor transmitting user traffic or control traffic may be used between theeNBs 20. The MME/SAE gateway 30 provides an endpoint of a session andmobility management function to the UE 10. The eNB 20 and the MME/SAEgateway 30 may be connected through an S1 interface.

MME provides various functions such as distribution of a paging messageto the eNBs 20, security control, idle state mobility control, SAEbearer control and encryption and integrity protection of non-accessstratum (NAS) signaling. The SAE gateway host provides various functionsincluding user plane switching for plane packet completion and mobilitysupport of the UE 10. The MME/SAE gateway 30 is briefly referred to as agateway in the present specification. However, the MME/SAE gateway 30includes both the MME gateway and the SAE gateway.

A plurality of nodes may be connected between the eNB 20 and the gateway30 through an S1 interface. The eNBs 20 may be connected to each otherthrough an X2 interface and neighboring eNBs may have a mesh networkstructure employing the X2 interface.

FIG. 2 is a diagram showing the structures of a general E-UTRAN and ageneral gateway 30. Referring to FIG. 2, the eNB 20 may performfunctions such as selection for the gateway 30, routing to the gatewayduring radio resource control (RRC) activation, scheduling andtransmission of a paging message, scheduling and transmission ofbroadcast channel (BCCH), dynamic resource allocation for UEs 10 inuplink/downlink, configuration and preparation of eNB measurement, radiobearer control, radio admission control (RAC) and connection mobilitycontrol in an LTE-ACTIVE state. The gateway 30 may perform functionssuch as paging transmission, LTE_IDLE state management, user planeencryption, system architecture evolution (SAE) bearer control andencryption and integrity protection of non-access stratum (NAS)signaling.

FIGS. 3A to 3B are diagrams showing a user-plane protocol andcontrol-plane protocol stack for an E-UMTS. Referring to FIGS. 3A to 3B,protocol layers may be divided into a first layer (L1), a second layer(L2) and a third layer (L3) based on a lower three layers of an opensystem interconnection (OSI) standard model known in a technical fieldof a communication system.

A physical (PHY) layer of a first layer (L1) provides an informationtransfer service to a higher layer using a physical channel. The PHYlayer is connected to a Medium Access Control (MAC) layer located on ahigher layer via a transport channel. Data is transported between theMAC layer and the PHY layer via the transport channel. Data is alsotransported between a physical layer of a transmitting side and aphysical layer of a receiving side via a physical channel.

A Medium Access Control (MAC) layer of a second layer (L2) provides aservice to a Radio Link Control (RLC) layer of a higher layer via alogical channel. The RLC layer of the second layer (L2) supportsreliable data transmission. If the MAC layer performs an RLC function,the RLC layer may be included as a functional block of the MAC layer. APacket Data Convergence Protocol (PDCP) layer of the second layer (L2)performs a header compression function. The header compression functionenables efficient transmission of an Internet Protocol (IP) packet suchas an IPv4 packet or an IPv6 packet in a radio interface having arelatively small bandwidth.

A Radio Resource Control (RRC) layer located at the bottom of a thirdlayer (L3) is defined only on the control plane and is responsible forcontrol of logical, transport, and physical channels in association withconfiguration, re-configuration, and release of Radio Bearers (RBs). TheRB means a service provided by the second layer (L2) for datacommunication between the UE and the E-UTRAN.

Referring to FIG. 3A, the RLC and MAC layers end at the eNB 20 and mayperform functions scheduling automatic repeat request (ARQ) and hybridautomatic repeat request (HARQ). The PDCP layer ends at the eNB 20 andmay perform functions such as header compression, integrity protectionand encryption.

Referring to FIG. 3B, the RLC and MAC layers end at the eNB 20 andperform the same functions as the control plane. As shown in FIG. 3A,the RRC layer ends at the eNB 20 and may perform functions such asbroadcasting, paging, RRC connection management, radio bearer (RB)control, mobility function and UE measurement report and control. TheNAS control protocol ends at the MME of the gateway 30 and may performfunctions such as SAE bearer management, authentication, LTE-IDLEmobility handling, paging transmission in an LTE_IDLE state and securitycontrol for signaling between the gateway and the UE 10.

The NAS control protocol may use three states. An LTE-DETACHED state isused when there is no RRC entity. An LTE_IDLE state is used when thereis no RRC connection while storing minimum UE 10 information. AnLTE_ACTIVE state is used when an RRC state is configured. The RRC stateis subdivided into an RRC_IDLE state and an RRC_CONNECTED state.

In the RRC_IDLE state, the UE 10 performs discontinuous reception (DRX)configured by NAS using a uniquely allocated ID in a tracking region.That is, the UE 10 may monitor a paging signal at a specific pagingoccasion per UE-specific paging DRX cycle to receive broadcast of systeminformation and paging information. In the RRC_IDLE state, the eNB doesnot store any RRC context.

In the RRC_CONNECTED state, the UE 10 may transmit and/or receive datato/from the eNB using context in the E-UTRAN and E-UTRAN RRC connection.In addition, the UE may report channel quality information and feedbackinformation to the eNB. In the RRC_CONNECTED state, the E-UTRAN knows acell, to which the UE 10 belongs. Accordingly, the network may transmitand/or receive data to/from the UE 10, control mobility such as UEhandover and perform cell measurement of peripheral cells.

FIG. 4 is a diagram showing the structure of a radio frame.

Referring to FIG. 4, the E-UMTS system uses a radio frame of 10 ms andone radio frame includes 10 subframes. In addition, one subframeincludes two consecutive slots. The length of one slot may be 0.5 ms.One subframe includes a plurality of symbols (e.g., OFDM symbols, SC-FDMsymbols). One subframe includes a plurality of resource blocks and oneresource block includes a plurality of symbols and a plurality ofsubcarriers. In downlink, some (e.g., first symbol) of the plurality ofsymbols configuring the subframe may be used to transmit L1/L2 controlinformation.

More specifically, a maximum of three (four) OFDM symbols of a frontportion of a first slot within a subframe corresponds to a controlregion to which a downlink control channel is allocated for L1/L2control information transmission. The remaining OFDM symbols correspondto a data region to which a Physical Downlink Shared Channel (PDSCH) isallocated. Examples of the downlink control channels include, forexample, a Physical Control Format Indicator Channel (PCFICH), aPhysical Downlink Control Channel (PDCCH), a Physical Hybrid automaticrepeat request Indicator Channel (PHICH), etc. The PCFICH is transmittedat a first OFDM symbol of a subframe, and carries information about thenumber of OFDM symbols used to transmit the control channel within thesubframe. The PHICH carries a HARQ ACK/NACK signal in response to uplinktransmission.

The control information transmitted through the PDCCH is referred to asDownlink Control Information (DCI). In the DCI format, formats 0, 3, 3Aand 4 are defined for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2Band 2C are defined for downlink. The DCI format selectively includeshopping flag, RB allocation, modulation coding scheme (MCS), redundancyversion (RV), new data indicator (NDI), transmit power control (TPC),cyclic shift demodulation reference signal (DM RS), channel qualityinformation (CQI) request, HARQ process number, transmitted precodingmatrix indicator (TPMI), precoding matrix indicator (PMI), etc.

The PDCCH may carry transmission format and resource allocationinformation of a Downlink Shared Channel (DL-SCH), transmission formatand resource allocation information of an Uplink Shared Channel(UL-SCH), paging information on a Paging Channel (PCH), systeminformation on the DL-SCH, resource allocation of a higher layer controlmessage such as a Random Access Response (RAR) transmitted on the PDSCH,a set of transmit (Tx) power control commands for individual UEs withina UE group, a Tx power control command, information indicatingactivation of Voice over IP (VoIP), etc. A plurality of PDCCHs may betransmitted within the control region. The UE may monitor the pluralityof PDCCHs. The PDCCHs are transmitted as an aggregate of one or severalconsecutive control channel elements (CCEs). The CCE is a logicalallocation unit used to provide the PDCCHs with a coding rate based onthe state of a radio channel. The CCE corresponds to a plurality ofresource element groups (REGs). The format of the PDCCH and the numberof PDCCH bits are determined based on the number of CCEs. The BSdetermines a PDCCH format according to a DCI to be transmitted to theUE, and attaches a Cyclic Redundancy Check (CRC) to control information.The CRC is masked with a Radio Network Temporary Identifier (RNTI)according to an owner or usage of the PDCCH. If the PDCCH is for aspecific UE, a cell-RNTI (C-RNTI) of the UE may be masked to the CRC.Alternatively, if the PDCCH is for a paging message, a paging indicatoridentifier (P-RNTI) may be masked to the CRC. If the PDCCH is for systeminformation (more specifically, a system information block (SIB)), asystem information RNTI (SI-RNTI) may be masked to the CRC. If the PDCCHis for random access response, a random access-RNTI (RA-RNTI) may bemasked to the CRC.

FIG. 5 is a diagram showing the structure of an uplink subframe.

Referring to FIG. 5, a subframe having a length of 1 ms includes two ofslots each having a length of 0.5 ms. The slot may include SC-FDMAsymbols, the number of which is changed according to CP length. Forexample, the slot includes seven SC-FDMA symbols in a normal CP case andincludes six SC-FDMA symbols in an extended CP case. A resource block503 is a resource allocation unit corresponding to 12 subcarriers in afrequency domain and one slot in a time domain. The structure of theuplink subframe may be divided into a control region 504 and a dataregion 505. The data region includes a PUSCH and is used to transmit adata signal such as voice. The control region includes a PUCCH and isused to transmit uplink control information (UCI). The PUCCH includes anRB pair located at both ends of the data region on a frequency axis andis hopped at a slot boundary.

The PUCCH may be used to transmit the following control information.

-   -   Scheduling request (SR): Information used to request uplink        (UL)-SCH resources. This is transmitted using an on-off keying        (OOK) method.    -   HARQ ACK/NACK: Response signal to downlink data packets. This        indicates whether downlink data packets have been successfully        received. 1-bit ACK/NACK is transmitted in response to a single        downlink codeword and 2-bit ACK/NACK is transmitted in response        to two downlink codewords.    -   Channel quality information (CQI): Feedback information for a        downlink channel (e.g., channel quality indicator (CQI)).        Multiple input multiple output (MIMO)-related feedback        information includes a rank indicator (RI), a precoding matrix        indicator (PMI) and a precoding type indicator (PTI). 20 bits        are used per subframe. Periodic CSI (p-CSI) is periodically        transmitted via a PUCCH according to period/offset configured by        a higher layer. In contrast, aperiodic CSI (a-CSI) is        aperiodically transmitted via a PUSCH according to a command of        an eNB.

Table 1 shows a mapping relationship between PUCCH format and UCI inLTE/LTE-A.

TABLE 1 PUCCH format Uplink control information (UCI) Format 1Scheduling request (SR) (unmodulated waveform) Format 1a 1-bit HARQACK/NACK (SR presence/absence) Format 1b 2-bit HARQ ACK/NACK (SRpresence/absence) Format 2 CQI (20 coded bits) Format 2 CQI and 1- or2-bit HARQ ACK/NACK (20 bits) (only extended CP) Format 2a CQI and 1-bitHARQ ACK/NACK (20 + 1 coded bits) Format 2b CQI and 2-bit HARQ ACK/NACK(20 + 2 coded bits) Format 3 HARQ ACK/NACK + SR (48 bits) (LTE-A)

A/N transmission and CSI transmission may be required on the samesubframe. In this case, if A/N+CSI simultaneous transmissionnon-permission is configured at a higher layer(“Simultaneous-AN-and-CQI” parameter=OFF), A/N transmission is onlyperformed using PUCCH format 1a/1b and CSI transmission is dropped. Incontrast, if A/N+CQI simultaneous transmission permission is configured(“Simultaneous-AN-and-CQI” parameter=ON), A/N and CQI are simultaneouslytransmitted via PUCCH format 2/2a/2b. More specifically, in a normal CPcase, A/N is embedded in a second RS of each slot (an RS is multipliedby A/N) in PUCCH format 2a/2b. In an extended CP case, A/N and CQI arejointly coded and then transmitted via PUCCH format 2.

FIG. 6 is a diagram showing a slot level structure of physical uplinkcontrol channel (PUCCH) format 1a/1b. The structure of PUCCH format 1used for SR transmission is equal to the structure of PUCCH format1a/1b.

Referring to FIG. 6, 1-bit [b(0)] A/N information and 2-bit [b(0)b(1)]A/N information are respectively modulated according to a binary phaseshift keying (BPSK) modulation scheme and a quadrature phase shiftkeying (QPSK) modulation scheme, and one A/N modulation symbol isgenerated (d₀). In A/N information, each bit [b(i), 1] indicates a HARQresponse to a transport block, is 1 in case of positive ACK and is 0 incase of negative ACK (NACK). Table 4 shows a modulation table for PUCCHformats 1a and 1b in legacy LTE.

TABLE 2 PUCCH format b(0), . . . , b(M_(bit) − 1) d(0) 1a 0  1 1 −1 1b00  1 01 −j 10  j 11 −1

In PUCCH format 1a/1b, cyclic shift (CS) (α_(cs,X)) is performed in thefrequency domain and spreading is performed using an orthogonal code(OC) (e.g., Walsh-Hadamard or DFT code) (w₀, w₁, w₂, w₃) in the timedomain.

FIG. 7 is a diagram showing PUCCH format 2/2a/2b.

Referring to FIG. 7, if a normal CP is configured, PUCCH format 2/2a/2bincludes five QPSK data symbols and two RS symbols at a slot level. Ifan extended CP is configured, PUCCH format 2/2a/2b includes five QPSKdata symbols and one RS symbol at a slot level. If an extended CP isconfigured, an RS symbol is located at a fourth SC-FDMA symbol of eachslot. Accordingly, PUCCH format 2/2a/2b may carry a total of 10 QPSKdata symbols. Each QPSK symbol is spread in the frequency domain by a CSand then is mapped to an SC-FDMA symbol. The RS may be multiplexed bycode division multiplexing (CDM) using a CS.

FIG. 8 is a diagram showing a random access procedure.

Referring to FIG. 8, a UE receives random access information from an eNBvia system information. Thereafter, if random access is necessary, theUE transmits a random access preamble (message 1) to the eNB (S810).When the eNB receives the random access preamble from the UE, the eNBtransmits a random access response message (RAR) (message 2) to the UE(S820). More specifically, downlink scheduling information of the randomaccess response message may be CRC-masked with a random access RNTI(RA-RNTI) and transmitted on an L1/L2 control channel (PDCCH). A PDCCHmasked with the RA-RNTI (hereinafter, RAR-PDCCH) is transmitted in acommon search space. The UE, which has received a downlink schedulingsignal masked with the RA-RNTI, may receive the random access responsemessage from a scheduled PDSCH and decode the random access responsemessage. Thereafter, the UE checks whether random access responseinformation signaled thereto is included in the random access responsemessage. Whether the random access response information signaled theretois included may be checked by determining whether a random accesspreamble ID (RAID) for the preamble transmitted by the UE is present.The random access response information includes timing advance (TA)indicating timing offset information for synchronization, radio resourceallocation information used for uplink, a temporary identifier for UEidentification (e.g., temporary C-RNTI, TC-RNTI). When the UE receivesthe random access response information, an uplink message (message 3) istransmitted via an uplink shared channel (SCH) according to the radioresource allocation information included in the response information(S830). The eNB receives the uplink message and then transmits acontention resolution (message 4) to the UE (S840).

FIG. 9 is a diagram showing an uplink-downlink timing relationship.

Referring to FIG. 9, at the UE, transmission of uplink radio frame #imay start at a point of time earlier than a point of time whentransmission of a downlink radio frame corresponding thereto starts by(N_(TA)+N_(TAoffset))×T_(s). Here, 0≦N_(TA)≦20512, N_(TAoffset)=0 in FDDand N_(TAoffset)=624 in TDD. N_(TA) is indicated by a timing advance(TA) command and the UE adjusts transmission timing of an uplink signal(e.g., PDCCH, PUSCH, SRS, etc.) by (N_(TA)+N_(TAoffset))×TS. ULtransmission timing may be adjusted in units of 16T_(s). T_(s) is asampling time. The TA command included in the RAR has 11 bits, indicatesvalues of 0 to 1282 and N_(TA)=TA*16. In the other case, the TA commandhas 6 bits, indicates values of 0 to 63 and is given withN_(TA)=N_(TA,old)(TA−31)*16. The TA command TAC received on subframe #nis applied after subframe #n+6.

FIG. 10 is a diagram showing a handover procedure.

Referring to FIG. 10, a UE 10 transmits a measurement report to a sourceeNB 20 (S102). The source eNB 20 transmits a handover request message toa target eNB along with UE 10 context (S104). The target eNB 20transmits a handover request response to the source eNB (S106). Thehandover request response includes a new C-RNTI, a part of handovercommand message and a dedicated preamble index for contention-freerandom access in a target cell. The source eNB 20 transmits a handovercommand to the UE (S108). The handover command includes a new C-RNTI andinformation related to random access such as a dedicated preamble indexto be used by the UE 10. The random access procedure is performed in thetarget cell after a handover command in order for the UE 10 to acquire atiming advance (TA) value. The random access procedure is acontention-free procedure in which a preamble index is reserved for theUE 10 in order to avoid collision. The UE 10 transmits a random accesspreamble using a dedicated preamble index such that the target eNB 20starts the random access procedure (S110). The target eNB 20 transmits arandom access response message to the UE 10 (S112). The random accessresponse message includes TA and uplink resource assignment. The UE 10transmits a handover complete message to the target eNB 20 (S114).

FIG. 11 is a diagram showing an example of determining a PUCCH resourcefor acknowledgement/negative acknowledgement (ACK/NACK) transmission. Inan LTE/LTE-A system, the PUCCH resource for A/N is not allocated to eachUE in advance and a plurality of PUCCH resources is divided and used bya plurality of UEs in a cell at every point of time. More specifically,the PUCCH resource used for the UE to transmit A/N corresponds to aPDCCH carrying scheduling information of downlink data or a PDCCHindicating SPS release. A PDCCH transmitted to the UE on a downlinksubframe is composed of one or more control channel elements (CCEs). TheUE may transmit A/N via PUCCH resources corresponding to a specific CCE(e.g., a first CCE) among the CCEs configuring the PDCCH. As shown inFIG. 11, if it is assumed that information on the PDSCH is transmittedvia a PDCCH composed of fourth to sixth CCEs, the UE transmits A/N usinga PUCCH resource index 4 corresponding to a CCE 4 which is a first CCEconfiguring the PDCCH.

More specifically, in LTE/LTE-A, the PUCCH resource index is determinedas follows.n ⁽¹⁾ _(PUCCH) =n _(CCE) +N ⁽¹⁾ _(PUCCH)  Equation 1

where, n⁽¹⁾ _(PUCCH) denotes a resource index of PUCCH format 1a/1b fortransmitting ACK/NACK/DTX, N⁽¹⁾ _(PUCCH) denotes a signaling valuereceived from a higher layer and n_(CCE) denotes the smallest valueamong CCE indices used for PDCCH transmission. Cyclic shift (CS),orthogonal code (OC) and physical resource block (PRB) for PUCCH format1a/1b are obtained from n⁽¹⁾ _(PUCCH).

Since an LTE UE cannot simultaneously transmit a PUCCH and a PUSCH, ifUCI (e.g., CQI/PMI, HARQ-ACK, RI, etc.) needs to be transmitted on asubframe on which a PUSCH is transmitted, the UCI is multiplexed in aPUSCH region (PUSCH piggybacking). Even in LTE-A, the UE may beconfigured not to simultaneously transmit a PUCCH and a PUSCH. In thiscase, if UCI (e.g., CQI/PMI, HARQ-ACK, RI, etc.) needs to be transmittedon a subframe on which a PUSCH is transmitted, the UCI is multiplexed ina PUSCH region (PUSCH piggybacking).

FIG. 12 is an ACK/NACK transmission procedure in a single cellsituation.

Referring to FIG. 12, a UE may receive one or more DL transmissions(e.g., PDSCH signals) on M DL subframes (SFs) (S502_0 to S502_M−1). EachPDSCH signal is used to transmit one or a plurality (e.g., 2) oftransmission blocks (TBs) (or codewords (CWs)) according to atransmission mode (TM). In addition, although not shown, in steps S502_0to S502_M−1, a PDCCH signal requesting an ACK/NACK response, e.g., aPDCCH signal indicating SPS release (an SPS release PDCCH signal) mayalso be received. If a PDSCH signal and/or an SPS release PDCCH signalis present in M DL subframes, the UE transmits A/N via one UL subframecorresponding to M DL subframes via a procedure of transmitting A/N(e.g., A/N (payload) generation, A/N resource allocation, etc.) (S504).A/N includes reception response information of the PDSCH signal and/orthe SPS release PDCCH of steps S502_0 to S502_M−1. Although A/N isbasically transmitted via a PUCCH (for example, see FIGS. 6 to 7), A/Nmay be transmitted via a PUSCH if a PUSCH is transmitted when A/N istransmitted. For A/N transmission, various PUCCH formats of Table 1 maybe used. In order to reduce the number of transmitted A/N bits, variousmethods such as A/N bundling, A/N channel selection, etc. may be used.

M=1 in FDD and M is an integer of 1 or more in TDD. In TDD, arelationship between M DL subframes and a UL subframe on which A/N istransmitted is given by a downlink association set index (DASI).

Table 3 shows a DASI (K: {k₀, k₁, . . . , k_(M-1)}) defined inLTE/LTE-A. If a PDSCH transmission and/or SPS release PDCCH is presentin a subframe n-k (kεK), the UE transmits ACK/NACK corresponding theretoon a subframe n.

TABLE 3 UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, 6— — 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 11 6, 5, 4, 7 — —— — — — 5 — — 13, 12, 9, 8, 7, 5, 4, 11, 6 — — — — — — — 6 — — 7 7 5 — —7 7 —

Upon operation using a TDD scheme, the UE should transmit an A/N signalfor one or more DL transmissions (e.g., PDSCH), which are received via MDL SFs, via one UL SF. A method for transmitting A/N for a plurality ofDL SFs via one UL SF will now be described.

1) A/N bundling: A/N bits for a plurality of data units (e.g., a PDSCH,an SPS release PDCCH, etc.) are combined by a logical operation (e.g.,logical-AND operation). For example, when all data units aresuccessfully decoded, a receiver (e.g., the UE) transmits an ACK signal.In contrast, when any one of the data units fails to be decoded (ordetected), the receiver transmits a NACK signal or does not transmit asignal.

2) Channel selection: The UE, which has received a plurality of dataunits (e.g., a PDSCH, an SPS release PDCCH, etc.), occupies a pluralityof PUCCH resources for A/N transmission. An A/N response to theplurality of data units is identified by a combination of PUCCHresources used for actual A/N transmission and transmitted A/Ninformation (e.g., a bit value, a QPSK symbol value, etc.). A channelselection method is also referred to as an A/N selection method or aPUCCH selection method.

FIG. 13 is a diagram showing a carrier aggregation (CA) communicationsystem. An LTE-A system uses carrier aggregation or bandwidthaggregation technology to aggregate a plurality of uplink/downlinkfrequency blocks to use a larger uplink/downlink bandwidth in order touse a wider frequency bandwidth. Each frequency block is transmittedusing a component carrier (CC). The component carrier may be understoodas a carrier frequency (or a center carrier or a center frequency) for afrequency block.

Referring to FIG. 13, a plurality of uplink/downlink component carriers(CCs) may be aggregated to support a wider uplink/downlink bandwidth.CCs may or may not be adjacent to each other in the frequency domain.The bandwidth of each CC may be independently configured. Asymmetriccarrier aggregation in which the number of UL CCs and the number of DLCCs are different is possible. For example, if the number of DL CCs is 2and the number of UL CCs is 1, the DL CCs may correspond to the UL CC2:1. The DL CC/UL CC link may be fixed or semi-static. In addition,although an overall system bandwidth includes N CCs, a frequencybandwidth monitored/received by a specific UE may be restricted to L(<N) CCs. Various carrier aggregation parameters may be configured in acell-specific, UE group-specific or UE-specific manner. Controlinformation may be configured to be transmitted and received only via aspecific CC. Such a specific CC may be referred to as a primary CC (PCC)and the remaining CCs may be referred to as secondary CCs (SCCs).

LTE-A uses the concept of a cell in order to manage radio resources. Thecell is defined as a combination of downlink resources and uplinkresources, and the uplink resources are not mandatory. Accordingly, thecell may be composed of downlink resources alone or both downlinkresources and uplink resources. If carrier aggregation is supported,linkage between a carrier frequency (or a DL CC) of downlink resourcesand a carrier frequency (or a UL CC) of uplink resources may beindicated by system information. A cell operating on a primary frequency(e.g., a primary CC (PCC)) may be referred to as a PCell and a celloperating on a secondary frequency (e.g., a secondary CC (SCC)) may bereferred to as an SCell. The PCell is used for a UE to perform aninitial connection establishment procedure or a connectionre-establishment procedure. The PCell may indicate a cell indicated in ahandover procedure. The SCell may be configured after RRC connectionestablishment and may be used to provide additional radio resources. ThePCell and the SCell may be collectively referred to as a serving cell.In the case of a UE which is in an RRC_CONNECTED state but does notestablish or support carrier aggregation, only one serving cellincluding only the PCell exists. In case of a UE which is in anRRC_CONNECTED state and establishes carrier aggregation, one or moreserving cells exist and the serving cells include the PCell and allSCells. For carrier aggregation, a network may be added to the PCellinitially configured in a connection establishment procedure and one ormore SCells may be configured for a UE supporting carrier aggregation,after an initial security activation procedure is initiated.

If cross-carrier scheduling (or cross-CC scheduling) is applied, a PDCCHfor downlink allocation is transmitted on DL CC #0 and a PDSCHcorresponding thereto is transmitted on DL CC #2. For cross-CCscheduling, a carrier indicator field (CIF) may be introduced.Presence/absence of a CIF within a PDCCH may be configured by higherlayer signaling (e.g., RRC signaling) in a semi-static and UE-specific(or UE group-specific) manner. A baseline of PDCCH transmission will besummarized as follows.

-   -   CIF disabled: A PDCCH on a DL CC allocates PDSCH resources on        the same DL CC or PUSCH resources on a single linked UL CC.    -   CIF enabled: A PDCCH on a DL CC may allocate PDSCH or PUSCH        resources on a specific DL/UL CC among a plurality of aggregated        DL/UL CCs using a CIF.

If the CIF is present, an eNB may allocate a PDCCH monitoring DL CC setin order to reduce BD complexity of a UE. The PDCCH monitoring DL CC setis a part of all aggregated DL CCs and includes one or more DL CCs. A UEperforms PDCCH detection/decoding only on the DL CC. That is, if an eNBschedules a PDSCH/PUSCH to a UE, the PDCCH is transmitted only via aPDCCH monitoring DL CC set. The PDCCH monitoring DL CC set may beconfigured in a UE-specific, UE group-specific or cell-specific manner.The term “PDCCH monitoring DL CC” may be replaced with the term“monitoring carrier” or “monitoring cell”. In addition, the term “CCsaggregated for a UE” may be replaced with the term “serving CC”,“serving carrier” or “serving cell”.

FIG. 14 shows scheduling if a plurality of carriers is aggregated.Assume that three DL CCs are aggregated. Assume that a DL CC A isconfigured to a PDCCH monitoring DL CC. DL CCs A to C may be referred toas serving CCs, serving carriers or service cells. If a CIF is disabled,each DL CC may transmit only a PDCCH scheduling a PDSCH thereof withoutthe CIF according to an LTE PDCCH rule. In contrast, if a CIF is enabledby UE-specific (or UE group-specific or cell-specific) higher layersignaling, the DL CC A (monitoring DL CC) may transmit not only a PDCCHscheduling a PDCCH of the DL CC A but also a PDCCH scheduling a PDSCH ofanother CC, using the CIF. In this case, the PDCCH is not transmitted inthe DL CC B/C.

FIG. 15 is a diagram showing an example of allocating a downlinkphysical channel to a subframe.

Referring to FIG. 15, a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE/LTE-A may be allocated to a control region (seeFIG. 4) of a subframe. In the figure, the L-PDCCH region means a regionto which a legacy PDCCH may be allocated. Meanwhile, a PDCCH may befurther allocated to the data region (e.g., a resource region for aPDSCH). A PDCCH allocated to the data region is referred to as anE-PDCCH. As shown, control channel resources may be further acquired viathe E-PDCCH to mitigate a scheduling restriction due to restrictedcontrol channel resources of the L-PDCCH region. Similarly to theL-PDCCH, the E-PDCCH carries DCI. For example, the E-PDCCH may carrydownlink scheduling information and uplink scheduling information. Forexample, the UE may receive the E-PDCCH and receive data/controlinformation via a PDSCH corresponding to the E-PDCCH. In addition, theUE may receive the E-PDCCH and transmit data/control information via aPUSCH corresponding to the E-PDCCH. The E-PDCCH/PDSCH may be allocatedstarting from a first OFDM symbol of the subframe, according to celltype.

FIG. 16 is a diagram showing a medium access control protocol data unit(MAC PDU). The MAC PDU is transmitted via a downlink shared channel(DL-SCH) and an uplink shared channel (UL-SCH).

Referring to FIG. 16, the MAC PDU includes a MAC header, 0 or more MACservice data units (SDUs) and 0 or more MAC control elements (CEs). AMAC PDU subheader has the same order as the MAC SDU and MAC CEcorresponding thereto. The MAC CE is located in front of the MAC SDU.The MAC CE is used to carry a variety of MAC control information. Forexample, the MAC CE includes SCell activation/deactivation information,TAC information, buffer status report (BSR) information and powerheadroom report (PHR) information.

FIG. 17 is a diagram showing an SCell activation/deactivation MACcontrol element (CE). An eNB may individually activate or deactivate theSCell with respect to all SCell aggregated for the UE using theactivation/deactivation MAC CE. Meanwhile, a PCell is always activated.

Referring to FIG. 17, the activation/deactivation MAC CE is identifiedby the MAC PDU having a logical channel identifier (LCID) (e.g.,LCID=11011) indicating activation/deactivation. Theactivation/deactivation MAC CE is composed of a single octet havingseven C-fields and one R-field.

-   -   C_(i): Indicates the activation/deactivation state of the SCell        having ScellIndex i. If there is no SCell having ScellIndex i,        the UE ignores the C_(i) field. The C_(i) field is set to 1 if        activation is indicated and is set to 0 if deactivation is        indicated.    -   R: Reserved bit. This is set to 0.

FIG. 18 is a diagram showing a timing advance command (TAC) MAC CE. TheeNB may adjust uplink timing per TAG with respect to all TAGs configuredfor the UE using a TAC MAC CE. The TAC MAC CE includes a TAG identity(ID) field and a TAC field.

-   -   TAG: Indicates a TAG. TAG ID=0 in the case of a TAG including a        PCell.    -   TAC: Indicates the amount of timing to be adjusted by the UE.        This has 6 bits and indicates values of 0 to 63. For a detailed        description thereof, refer to FIG. 9.

FIG. 19 is a diagram showing a power headroom report (PHR) MAC CE. FIG.19 shows an extended PH MAC CE and may notify the UE of a PH foraggregated all cells. The field of the PH MAC CE will now be described.

-   -   C_(i): Indicates whether a PH field for an SCell having        ScellIndex i is present. The C_(i) field is set to 1 if the PH        field for the SCell having ScellIndex i is reported and,        otherwise, is set to 0.    -   R: Reserved bit. This is set to 0.    -   V: Indicates whether the PH value is based on actual        transmission or reference format.    -   PH: Indicates a power headroom level.    -   P: Indicates whether the UE applies power backoff for power        management.    -   P_(CMAC,c): Indicates information about per-cell maximum power        used to calculate the value of the above-described PH field.

Embodiment: Signaling in Inter-Site CA

In LTE-A, assume that aggregation (that is, CA) of a plurality of cellsis supported and a plurality of cells aggregated for one UE is managedby one eNB (intra-site CA). In intra-site CA, since all cells aremanaged by one eNB, signaling related to various RRCconfigurations/reports and MAC commands/messages may be performed viaany one of all aggregated cells. For example, signaling involved in aprocedure of adding or releasing a specific SCell to or from a CA cellset, a procedure of changing a transmission mode (TM) of a specificcell, a procedure of performing radio resource management (RRM)measurement reporting associated with a specific cell, etc. may beperformed via any cell of the CA cell set. As another example, signalinginvolved in a procedure of activating/deactivating a specific SCell, abuffer status report for UL buffer management, etc. may be performed viaany cell of the CA cell set. As another example, a per-cell powerheadroom report (PHR) for UL power control, a per-timing advanced group(TAG) timing advance command (TAC) for UL synchronization control, etc.may be signaled via any cell of the CA cell set.

Meanwhile, in a next-generation system subsequent to LTE-A, a pluralityof cells (e.g., micro cells) having small coverage may be deployed in acell (e.g., a macro cell) having large coverage, for trafficoptimization. For example, a macro cell and a micro cell may beaggregated for one UE, the macro cell may be mainly used for mobilitymanagement (e.g., PCell) and the micro cell may be mainly used forthroughput boosting (e.g., SCell). In this case, the cells aggregatedfor one UE may have different coverages and may be respectively managedby different eNBs (or nodes (e.g., relays) corresponding thereto) whichare geographically separated from each other (inter-site CA).

FIG. 20 is a diagram showing inter-site carrier aggregation (CA).Referring to FIG. 20, a method for performing radio resource control andmanagement for a UE (e.g., all functions of RRC and some functions ofMAC) at an eNB for managing a PCell (e.g., CC1) and performing datascheduling and feedback with respect to each cell (that is, CC1 or CC2)(e.g., all functions of PHY and main functions of MAC) at each eNB formanaging each cell may be considered. Accordingly, in inter-site CA,information/data exchange/delivery between cells (that is, between eNBs)is required. Upon considering a conventional signaling method, ininter-site CA, information/data exchange/delivery between cells (thatis, between eNBs) may be performed via a backhaul (BH) link (e.g., awired X2 interface or a wireless backhaul link). However, when theconventional method is applied without change, cell managementstability, resource control efficiency and data transmission adaptation,etc. may be considerably reduced due to latency caused in an inter-eNBsignaling procedure.

For example, as shown in FIG. 20, an inter-site CA situation in which aPCell (e.g., CC1) and an SCell (e.g., CC2) aggregated for one UE arerespectively managed by eNB-1 and eNB-2 is assumed. In addition, assumethat the eNB (that is, eNB-1) for managing the PCell is responsible formanaging/performing an RRC function associated with the UE correspondingthereto. At this time, if a radio resource management (RRM) measurement(e.g., reference signal received power (RSRP), reference signal receivedquality (RSRQ)) report associated with the SCell is not transmitted bythe PCell but is transmitted via the SCell (e.g., a PUSCH), eNB-2 maydeliver the RRM measurement report to eNB-1 via the BH. In addition,based on the RRM report, for example, if eNB-1 sends an RRCreconfiguration command for releasing the SCell from the CA cell set tothe UE via the PCell (e.g., a PDSCH), the UE may transmit a confirmationresponse to the RRC reconfiguration command via the SCell (e.g., aPUSCH) instead of the PCell. In this case, eNB-2 may deliver theconfirmation response to eNB-1 via the BH, etc. Accordingly, ininter-site CA, considerable latency may be caused in an inter-cell (thatis, inter-eNB) signaling procedure. Thus, misalignment between the eNBand the UE for CA cell set interpretation may occur and stable/efficientcell resource management and control may not be facilitated.

As another example, in the same inter-site CA situation, per-cell PHRsof all cells may be transmitted via the PCell (e.g., the PUSCH). In thiscase, eNB-1 (for managing the PCell) may deliver the PHR correspondingto all PHRs or a PHR corresponding to the SCell to eNB-2 (for managingthe SCell) via the BH, etc. In contrast, if per-cell PHRs of all cellsare transmitted via the SCell, eNB-2 may deliver all PHRs or a PHRcorresponding to the PCell to eNB-1 via the BH, etc. Even at this time,stable/efficient UL power control and adaptive UL datascheduling/transmission based thereon may not be facilitated due tolatency caused by inter-eNB signaling.

In order to solve the above-described problems, in an inter-site CAsituation or a CA situation similar thereto, configuring of a path inwhich specific signaling (e.g., RRC, MAC, DCI, UCI) associated with aspecific cell may be performed (e.g., a cell or cell group in which atransmission/reception operation for signaling may be performed) isproposed. For example, a path (e.g., a cell or cell group) in which asignal/channel transmission and/or reception operation involved inspecific signaling associated with a specific cell may be performed maybe configured. In this case, the UE may operate in a state in which thesignal/channel involved in specific signaling associated with thespecific cell may be transmitted and/or received only through theconfigured path. For example, the procedure ofreceiving/detecting/monitoring/decoding and/or transmitting/encoding thesignal/channel involved in specific signaling associated with thespecific cell is performed only on the configured path and may beomitted on the other paths. In the present invention, the specific cellincludes a cell or a cell group. A plurality of aggregated cells may bedivided into one or more cell groups. Here, each cell group is composedof one or more cells. For convenience, a cell group, to which a PCellbelongs, is referred to as a PCell group and a cell group includingSCells only is referred to as an SCell group. The number of PCell groupsmay be one and the number of SCell groups may be 0 or one or more. Inthe present specification, unless stated otherwise, the PDCCH mayinclude an L-PDCCH and an E-PDCCH.

A signaling method/path proposed by the present invention is applicableto only an inter-site CA situation or a CA situation similar thereto.That is, the signaling method/path proposed by the present invention isnot applied but a conventional signaling/path is applied to an intra-CAsituation. Accordingly, an eNB may notify a UE of configurationinformation of a signaling method/path via an RRC message, etc.Meanwhile, the eNB may consider a CA mode (that is, inter-site CA orintra-site CA) in order to configure the signaling method/path. However,the UE needs to know the applied signaling method/path only.Accordingly, the eNB may not notify the UE of a CA mode but notify theUE of information indicating the signaling method/path applied to the UEonly. Since the UE can know the signaling method/path applied theretofrom the CA mode, the eNB may not separately notify the UE of theinformation indicating the signaling method/path.

In the present invention, signaling subjected to path configuration mayinclude the following.

-   -   Command/response involved in an RRC        configuration/reconfiguration (e.g., SCell allocation/release,        per-cell TM configuration, per-cell CSI feedback mode/SRS        parameter configuration) procedure    -   Radio link monitoring (RLM) (e.g., radio link failure (RLF)) and        RRM measurement (e.g., RSRP, RSRQ) related configuration/report    -   handover (HO) related command response    -   MAC activation/deactivation (that is, SCell Act/De) message for        SCell    -   PHR, BSR, TAC    -   DCI (e.g., DL/UL grant), scheduling request (SR)    -   Periodic CSI (p-CSI) report, aperiodic CSI (a-CSI)        request/report    -   ACK/NACK (A/N) feedback to DL data reception    -   Random Access response (RAR), PDCCH for scheduling a PDSCH        carrying an RAR (hereinafter, RAR-PDCCH)

As a path configuration example according to signaling, a path forsignaling involved in an RRC reconfiguration procedure of additionallyallocating/releasing a specific cell to or from a CA cell set and an RRMmeasurement (e.g., RSRP, RSRQ) report associated with a specific cellmay be configured to a PCell group. In this case, signaling involved inan RRC reconfiguration/measurement report associated with a specificcell may be transmitted and received via the PCell group (a PDSCH/PUSCHof an arbitrary cell belonging thereto) only. In addition, a path inwhich a per-cell PHR for UL power control of a specific cell group (allcells belonging thereto) may be signaled may be configured to thespecific cell group. That is, a PHR for a specific cell group may betransmitted via the specific cell group (a PUSCH of an arbitrary cellbelonging thereto) only.

FIG. 21 is a diagram showing a signaling method according to oneembodiment of the present invention. Referring to FIG. 21, a path inwhich signaling associated with a specific cell in the situation shownin FIG. 20 is performed may be restricted to CC1 (group) or CC2 (group)according to signaling type. More specifically, in the presentinvention, a path configuration method according to signaling typeincludes the following.

Case #1

-   -   Signaling type: Command/response involved in an RRC        configuration/reconfiguration (e.g., SCell allocation/release,        per-cell TM configuration, per-cell CSI feedback mode/SRS        parameter configuration) procedure, RLM (e.g., RLF) and RRM        measurement (e.g., RSRP, RSRQ) related configuration/report,        handover (HO) related command/response    -   Signaling for a specific cell (or a specific cell group): A path        may be configured to a PCell group.

Case #2

-   -   Signaling type: MAC activation/deactivation message (that is,        SCell Act/De) for SCell, PHR, BSR, TAC, DCI (e.g., DL/UL grant),        aperiodic CSI (a-CSI) request/report    -   Signaling for a specific cell (or a specific cell group): A path        may be configured to a cell group, to which the specific cell        belongs, (or the specific cell group). In this case, signaling        may be restricted as follows.    -   A cell list to be activated/deactivated in SCell Act/De may be        composed of SCells belonging to the specific cell group only.    -   A PHR may be composed of a per-cell PHR belonging to the        specific cell group only. In addition, an independent PHR        transmission period may be configured per cell group.    -   A BSR may report a UL buffer status of the specific cell group        (all cells belonging thereto) only.    -   A TAC may be composed of per-TAG TACs belonging to the specific        cell group only. In addition, cells belonging to different cell        groups may not belong to the same TAG.    -   DCI may be scheduling/control information (e.g., DL/UL grant) of        cell(s) belonging to the specific cell group. In addition,        cross-CC scheduling may not be allowed between cells belonging        to different cell groups (that is, DCI (e.g., DL/UL grant)) for        a cell belonging to a specific cell group may be configured not        to be transmitted from a cell belonging to another cell group).    -   An a-CSI request/report may be an a-CSI request/report targeted        to cell(s) belonging to the specific cell group. In addition, an        a-CSI report target cell set designated via RRC signaling may be        independently configured per cell group (that is, an a-CSI        report target cell set, to which a-CSI request/report is        applied, in a specific cell group may be composed of cell(s)        belonging to the specific cell group only). In detail, the        number of bits configuring the a-CSI request field in DCI may be        independently configured according to the number of cells        belonging to the cell group (scheduled from the DCI) (for        example, to 1 bit if the number of cells is 1 and to 2 bits if        the number of cells is 2 or more). As another method, in order        to reduce RRC signaling overhead, the a-CSI request field in DCI        (scheduling the SCell group) is fixed to 1 bit with respect to        (all or a specific) SCell group, and an a-CSI report only for an        individual cell may be performed via a respective cell.

Case #3

-   -   Signaling type: ACK/NACK (A/N) for DL data, scheduling request        (SR), periodic CSI (p-CSI) report    -   Signaling for a cell belonging to a PCell group: If signaling        information is transmitted via a PUCCH, a path may be configured        to a PCell. If signaling information is transmitted via a PUSCH        (that is, piggybacked on PUSCH (multiplexed with UL data)), a        path may be configured to a PCell group (that is a PUSCH        transmission cell in a PCell group).    -   Signaling for a specific SCell belonging to an SCell group: If        signaling information is transmitted via a PUCCH, a path may be        configured to the specific SCell or a specific SCell designated        in the SCell group. (Here, in the designated specific SCell, for        example, one of cell(s) configured to perform PDCCH (e.g., DL/UL        grant) transmission or (DL/UL data) scheduling in the SCell        group is configured (via signaling) or a cell having a specific        (for example, smallest) index or specific (e.g., largest) system        bandwidth among cell(s) (here, cell(s) in which UL        resource/carrier is defined) may be automatically determined).        If signaling information is transmitted via a PUSCH (that is,        piggybacked on PUSCH (multiplexed with UL data)), a path may be        configured to the SCell group, to which the specific SCell        belongs. In this case, signaling may be restricted as follows.    -   A/N transmitted via a PUCCH of an SCell belonging to an SCell        group may be composed of an individual A/N response to DL data        reception in the SCell only. Unlike the PCell, since SCell        activation/deactivation is possible, if the PUCCH is transmitted        via a predefined SCell in the SCell group, a predefined SCell        may be deactivated when A/N transmission is necessary.        Accordingly, (in the case of the SCell group), A/N for the        SCell, which has received DL data, may be transmitted via the        SCell only. As another method, in order to reduce RRC signaling        overhead due to explicit PUCCH resource usage and allocation and        increase implicit PUCCH resource usage efficiency, A/N for DL        data reception in the specific SCell (belonging to the SCell        group) may be defined/set to be transmitted via a cell to which        a DL grant PDCCH scheduling the DL data is transmitted.

In addition, A/N piggybacked on a PUSCH of a specific SCell belonging tothe SCell group may be composed of an A/N response to DL data receptionin all cells of the SCell group.

-   -   An SR transmitted via a PUCCH of a specific SCell belonging to        the SCell group may be a UL scheduling request targeted to the        SCell group (all cells belonging thereto).    -   p-CSI transmitted via a PUCCH of a specific SCell belonging to        the SCell group may be restricted to p-CSI for the specific        SCell. In addition, p-CSI piggybacked on the PUSCH of the        specific SCell belonging to the SCell group may be composed of        p-CSI(s) for one or more cells in the SCell group.

Case #4

-   -   Signaling type: RAR, RAR-PDCCH    -   Signaling for PRACH transmission in a cell belonging to a PCell        group: A path of an RAR may be configured to a PCell and a path        of an RAR-PDCCH may be configured to a common search space of        the PCell.    -   Signaling for PRACH transmission in a specific SCell belonging        to an SCell group: A path of an RAR may be configured to the        specific SCell or a specific SCell designated in the SCell        group. A path of an RAR-PDCCH may be a common search space of        the specific SCell or a specific SCell designated in the SCell        group (here, in the case of the designated specific SCell, for        example, one of cell(s) configured to perform PDCCH (e.g., DL/UL        grant) transmission or (DL/UL data) scheduling in the SCell        group is configured (via signaling) or a cell having a specific        (for example, smallest) index or specific (e.g., largest) system        bandwidth among cell(s) (here, cell(s) in which UL        resource/carrier is defined) may be automatically determined).

Meanwhile, unlike the above examples, case #1 is applicable to SCellAct/De. In this case, a path in which MAC signaling related withactivation/deactivation of a specific SCell is performed may beconfigured to a PCell group.

In order to avoid simultaneous transmission of a plurality of PUCCHs, incase #3, the PUCCH transmitted via the SCell may be replaced with aPUSCH resource (hereinafter, a UCI-PUSCH resource) or a DMRS for PUSCHdemodulation (hereinafter, UCI-DMRS). UCI-PUSCH resources may beallocated for UCI transmission only (not for UL data transmission). TheUCI-PUSCH resource may include a PUSCH resource composed of one subframe(hereinafter, a normal PUSCH resource), a PUSCH resource composed of oneslot (hereinafter, a slot PUSCH resource) or a PUSCH resource composedof a small number of SC-FDMA symbols (hereinafter, a shortened PUSCHresource). The shortened PUSCH resource may be composed of N (e.g., N=2or 3)SC-FDMA symbols per slot, for example. In this case, in each slot,one or two SC-FDMA symbols may be used as DMRS transmission symbol andthe remaining one or two SC-FDMA symbols may be used as UCI transmissionsymbol. In addition, the shortened PUSCH resource composed of one slotmay be used as a UCI-PUSCH resource. Accordingly, a plurality ofshortened PUSCH resources may be multiplexed (using a TDM scheme) in oneUL resource block (RB) (pair).

Accordingly, the UCI-PUSCH resource may be identified by a UL RB index,a slot index (in a UL RB), an SC-FDMA symbol index, a CS and/or OCC(combination) index of a DMRS, etc. Although not limited thereto,individual UCI-PUSCH resources may be respectively allocated to A/N, SRand p-CSI; one common UCI-PUSCH resource may be allocated to all UCI; orone UCI-PUSCH resource may be allocated to two UCIs (e.g., A/N and SR)and one UCI-PUSCH resource may be allocated to the remaining one UCI(e.g., p-CSI). Here, the UCI-PUSCH resource may be allocated in advancevia RRC signaling. In addition, a plurality of UCI-PUSCH resources maybe allocated in advance via RRC signaling, etc. and a specific UCI-PUSCHresource of the plurality of UCI-PUSCH resources may be indicated via aDL grant PDCCH. More specifically, UCI-PUSCH resources may be indicatedvia a specific field (e.g., an A/N resource indicator (ARI) field) of aDL grant PDCCH. In addition, the UCI-PUSCH resource linked to a specificDL RB index (e.g., a lowest DL RB index) occupied by DL data may beallocated (in a state in which linkage between the downlink resourceblock (DL RB) resource and the UCI-PUSCH resource is designated/set). Inaddition, the UCI-PUSCH resource linked to a specific CCE index (e.g., alowest CCE index) constituting a PDCCH scheduling DL data may beallocated (in a state in which linkage between the CCE resource and theUCI-PUSCH resource is designated/set).

Next, a UCI-DMRS resource may be composed of M (e.g., M=1, 2, 3)SC-FDMAsymbols per slot. Unlike the shortened PUSCH resource, the M symbols ofthe UCI-DMRS resource may all be used as DMRS transmission symbols. Inaddition, a UCI-DMRS resource composed of one slot may be used for UCItransmission and thus a plurality of UCI-DMRS resources may bemultiplexed (using a TDM scheme) in one UL RB (pair). A UCI transmissionmethod using the UCI-DMRS resource may include 1) a method forselecting/transmitting different UCI-DMRS resources according to UCIvalue (e.g., ACK or NACK, positive or negative SR) (among a plurality ofUCI-DMRS resources) and 2) a method for transmitting a DMRS symbolmodulated (e.g., BPSK, QPSK) according to a UCI value on a UCI-DMRSresource (and/or a combination of 1) and 2)). In method 2), a specificDMRS symbol (e.g., a first DMRS symbol) in the UCI-DMRS resource may befixed without modulation (thus, a receiver (eNB) may receive UCIinformation via detection of a signal difference (e.g., a phasedifference) between a fixed DMRS symbol and a modulated DMRS symbol(similarly to existing PUCCH format 2a/2b for simultaneouslytransmitting CQI and A/N via differential modulation of a DMRS).

The UCI-DMRS resource may be identified by a UL RB index, a slot index(in a UL RB), an SC-FDMA symbol index, a CS and/or OCC (combination)index, etc. Individual or common UCI-DMRS resources may be allocated toA/N and SR only and UCI-PUSCH resources may be allocated to p-CSI. TheUCI-DMRS may be allocated in advance via RRC signaling, etc., or whichUCI-DMRS resource is used may be signaled via a PDCCH (e.g., an ARIfield in a PDCCH) in a state of allocating a plurality of UCI-DMRSresources in advance via RRC signaling or a UCI-DMRS resource linked toa specific CCE index (e.g., a lowest CCE index) configuring a PDCCHscheduling DL data or a specific DL RB index (e.g., a lowest DL RBindex) occupied by DL data (in a state in which linkage between the DLRB resource and the UCI-DMRS resource or between the CCE resource andthe UCI-DMRS resource is designated/set) may be allocated.

The signaling path configuring method of the present invention is notlimited to the above-described signaling types. For example, thesignaling path configuring method of the present invention is applicableto other signaling related to RRC/MAC/DCI/UCI. For example, case #1 isapplicable to signaling associated with an RRC layer, case #2 isapplicable to signaling associated with a MAC layer and case #3 isapplicable to signaling associated with DCI/UCI.

Meanwhile, a cell group may be differently designated/set according tosignaling or signaling set (that is, an independent cell group may bedesignated/configured according to signaling or signaling set). Thesignaling path configuring method of the present invention is applicablein a state in which cells having different frame structure types (e.g.,FDD or TDD) or cells having different CP lengths (e.g., normal CP orextended CP) are designated/set to belong to different cell group. Inthis case, if a cell group is designated (without a separate signalingpath configuring procedure), the signaling path configuring methods(case #1, #2, #3 and #4) of the present invention may be automaticallyapplied.

As another method, a method for configuring a cell via which signalingassociated with/related to/corresponding to a corresponding cell(signal/channel transmission and/or reception operation involvedtherein) may be performed (without separately designating/setting a cellgroup) may be considered for each cell. For example, in theabove-described signaling, the following per-cell path configuring maybe possible.

-   -   RRC configuration/reconfiguration    -   For each cell, a cell, via which command/response transmission        involved in an RRC configuration/reconfiguration procedure (such        as SCell allocation/release, per-cell TM configuration, per-cell        CSI feedback mode/SRS parameter configuration, etc.) of the        corresponding cell will be performed, may be configured.    -   RRM measurement    -   For each cell, a cell, via which RRM measurement related        configuration/report transmission (such as RSRP, RSRQ, etc.) of        the corresponding cell will be performed, may be configured.    -   RLM/HO    -   A cell, via which RLM related configuration/report and HO        related command/response transmission will be performed, may be        configured.    -   SCell activation/deactivation    -   For each cell, a cell, via which activation/deactivation message        transmission of the corresponding cell will be performed, may be        configured.    -   PHR/BSR/TAC    -   For each cell, a cell, via which PHR, BSR and TAC transmission        of the corresponding cell will be performed, may be configured.    -   DCI    -   For each cell, a cell, via which DCI transmission (of DL/UL        grant, etc.) of the corresponding cell will be performed, may be        configured.    -   SR    -   For each cell, a cell, via which SR transmission of the        corresponding cell will be performed, may be configured.    -   p-CSI report    -   For each cell, a cell, via which p-CSI report transmission of        the corresponding cell will be performed, may be configured.    -   a-CSI request/report    -   For each cell, a cell, via which a-CSI request/report        transmission of the corresponding cell will be performed, may be        configured.    -   ACK/NACK    -   For each cell, a cell, via which A/N feedback transmission for        DL data received via the corresponding cell will be performed,        may be configured.    -   RAR and RAR-PDCCH    -   For each cell, a cell, via which RAR and RAR-PDCCH transmission        corresponding to PRACH transmission of the corresponding cell        will be performed, may be configured.

As another method, in the case of HARQ-ACK for DL data, informationabout a cell and/or subframe via which HARQ-ACK transmission will beperformed may be indicated using DL grant DCI scheduling DL data inconsideration of coordination between cells (eNBs) for PUCCH and/or UCItransmission. More specifically, in a state of predefining/designating aplurality (e.g., 2) of cell/subframes (information) in advance, one of aplurality of cells/subframes via which HARQ-ACK transmission for DL datawill be performed may be indicated using DL grant DCI. The plurality ofcells may be defined/designated as the PCell and the cell via which DLgrant DCI (or DL data) is transmitted. The plurality of subframes may bedefined/designated as a HARQ-ACK transmission subframe (that is, anoriginal A/N SF) corresponding to DL grant DCI (or DL data) receptionsubframes (determined based on original HARQ-ACK timing defined in alegacy (e.g., Rel-10/11) FDD/TDD system) and an earliest UL SF (definedby HARQ timing) after the original A/N SF.

Similarly, even in the case of a PHICH for UL data, information about acell and/or subframe via which PHICH transmission will be performed maybe indicated using UL grant DCI scheduling UL data in considerationcoordination between cells (eNBs) for DL control resource transmission.More specifically, in a state of predefining/designating a plurality(e.g., 2) of cell/subframes (information) in advance, one of a pluralityof cells/subframes via which PHICH transmission for UL data will beperformed may be indicated using UL grant DCI. The plurality of cellsmay be defined/designated as the PCell and the cells via which UL grantDCI (or UL data) is transmitted. The plurality of subframes may bedefined/designated as a PHICH transmission subframes (that is, originalPHICH SF) corresponding to UL grant DCI (or UL data) reception subframe(determined based on PHICH timing) and an earliest DL (or special) SF(defined by PHICH timing) after the original PHICH SF.

Meanwhile, a backhaul link deployed for the purpose of exchange/deliveryof (UE related) information/data between cells (sites/eNBs formanaging/controlling the same) aggregated for one UE may be composed ofnon-ideal backhauls having significant latency. If cells (sites/eNBsmanaging/controlling the same) directly perform exchange/delivery of allinformation/data via the backhaul link in a non-ideal backhaul based CAsituation, significant load/latency may occur on the backhaul link. Inorder to solve this problem, it is proposed that informationexchange/delivery between cells is performed via the UE with respect toa specific/predetermined part of cell information in consideration ofload/latency on the backhaul link and a radio channel status of the UE.That is, the backhaul link between cells (sites/eNBs) may be replacedwith a radio link between the cell and the UE. More specifically,information exchange/delivery between cells aggregated for the UE may beperformed as follows via the radio link. For convenience, as shown inFIG. 21, assume that information related to a cell 1 is delivered to acell 2 via the UE in a state in which the cell 1 (e.g., CC1) and thecell 2 (e.g., CC2) are aggregated for the UE.

Alt 1: Cell 1 Command

-   -   The cell 1 may command/instruct the UE to deliver/report cell        1-related specific information to the cell 2 (via a specific DL        channel/signal transmitted on the cell 1).    -   The UE may deliver/report the cell 1-related specific        information to the cell 2 (via a specific UL channel/signal        transmitted on the cell 2) according to the command/instruction        of the cell 1.

Alt 2: UE Report

-   -   The UE may directly deliver/report the cell 1-related specific        information to the cell (via a specific UL channel/signal        transmitted on the cell 2) at a specific time or at a specific        period.    -   The specific time may be a time when the cell 1-related specific        information is reconfigured/changed (or an appropriate time        thereafter).    -   The specific period may be configured via L1/L2/RRC signaling        from the cell 1 or the cell 2.

Alt 3: Cell 2 Request

-   -   The cell 2 may request/instruct the UE to deliver/report the        cell 1-related specific information to the cell 2 (via a        specific DL channel/signal transmitted on the cell 2).    -   The UE may deliver/report the cell 1-related specific        information to the cell 2 (via a specific UL channel/signal        transmitted over on cell 2) according to the request/instruction        of the cell 2.

The cell-related specific information subjected to the above-describedinter-cell information signaling method may include at least a TMconfigured with respect to the corresponding cell, a CSI feedback mode,an SRS related parameter, an activation/deactivation state of thecorresponding cell, TA applied to the corresponding cell, etc. Morespecifically, in the case of Alt 1, the cell 1 may command/instruct theUE to deliver/report SRS related parameter information configured in thecell 1 (that is, configured in the cell 1 with respect to thecorresponding UE) to the cell 2. Thus, the UE may deliver/report the SRSrelated parameter information configured in the cell 1 to the cell 2. Inthe case of Alt 2, the UE may directly deliver/report TA informationapplied to the cell 1 to the cell 2 when TA applied to the cell 1 (thatis, TA information applied to the UE in the cell 1) isreconfigured/changed (or at an appropriate time thereafter). In the caseof Alt 3, the cell 2 may request/instruct the UE to deliver/reportactivation/deactivation state information of the cell 1 (that is,activation/deactivation applied to the cell 1 with respect to the UE) tothe cell 2. Then, the UE may deliver/report the activation/deactivationinformation of the cell 1 to the cell 2.

Meanwhile, in non-ideal backhaul based inter-site CA (or inter-eNB CA),[PCell, SCell]=[cell 1, cell 2] may be determined/set with respect tothe UE 1 and [PCell, SCell]=[cell 2, cell 1] may be determined/set withrespect to the UE 2. In addition, UE #3 may perform communication (thatis, signal/channel transmission and reception) only via one cell (thatis, the cell 1 or the cell 2). In this state, the eNB 1 may allocate aC-RNTI A to the UE 1 which uses/operates the cell 1, which ismanaged/controlled by the eNB 1, as the PCell and eNB 2 may allocate aC-RNTI B to the UE 2 which uses/operates the cell 2, which ismanaged/controlled by the eNB 1, as the PCell. In addition, the cell 2may be further allocated to the UE 1 as the SCell. At this time, whenthe C-RNTI A and the C-RNTI B have the same value, ambiguity may occurbetween the signal/channel of the UE 1 and the signal/channel of the UE2 over the cell 2 such that the transmission and reception operation maynot be normally performed. In this case, although the RNTI allocable tothe UE may be distributed per eNB (cell) in advance or informationexchange between eNBs may be performed in order to allocate RNTIs toUEs, this increases load/latency on the backhaul and deteriorate RNTIallocation efficiency.

Accordingly, in order to solve this problem, allocation/use of anindependent (same or different) RNTI to one UE per (aggregated) cell isproposed. For example, one UE for which the cell 1 and the cell 2 areaggregated may perform signal/channel transmission and reception usingthe C-RNTI A with respect to the cell 1 and perform signal/channeltransmission and reception using the C-RNTI B with respect to the cell2. At this time, the C-RNTI A and the C-RNTI B may have the same valueor different values. In addition, the UE may notify the cell 2 of theC-RNTI A information allocated/used to/by the cell 1 and notify the cell1 of the C-RNTI B information allocated/used to/by the cell 2. Here, thecell 1 and the cell 2 may be extended to a cell group 1 and a cell group2, respectively, and an independent RNTI may be allocated/used per cellgroup. The cell group may be composed of one or more cells and one RNTImay be allocated/used to/by all cells belonging to one cell group.Meanwhile, the RNTI allocated/used per cell may include at least one ofa system information-RNTI (SI-RNTI), paging RNTI (P-RNTI), a randomaccess RNTI (RA-RNTI), a cell RNTI (C-RNTI), a semi-persistentscheduling cell RNTI (SPS C-RNTI), a temporary C-RNTI, a transmit powercontrol-PUCCH-RNTI (TPC-PUCCH-RNTI), a TPC-PUSCH-RNTI and a MBMS RNTI(M-RNTI) and may preferably include a C-RNTI. The cell group may beequally or differently configured per RNTI.

FIG. 22 is a diagram showing a base station (BS) and a user equipment(UE) to which the present invention is applicable.

Referring to FIG. 22, a wireless communication system includes a basestation (BS) 110 and a UE 120. The BS 110 includes a processor 112, amemory 114 and a radio frequency (RF) unit 116. The processor 112 may beconfigured to implement the procedures and/or methods proposed by thepresent invention. The memory 114 is connected to the processor 112 soas to store a variety of information associated with operation of theprocessor 112. The RF unit 116 is connected to the processor 112 so asto transmit and/or receive an RF signal. The UE 120 includes a processor122, a memory 124 and an RF unit 126. The processor 122 may beconfigured to implement the procedures and/or methods proposed by thepresent invention. The memory 124 is connected to the processor 122 soas to store a variety of information associated with the operation ofthe processor 122. The RF unit 126 is connected to the processor 122 soas to transmit and/or receive an RF signal. The BS 110 and/or the UE 120may have a single antenna or multiple antennas.

The above-described embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered optional factors on the conditionthat there is no additional remark. If required, the individualconstituent components or characteristics may not be combined with othercomponents or characteristics. Also, some constituent components and/orcharacteristics may be combined to implement the embodiments of thepresent invention. The order of operations disclosed in the embodimentsof the present invention may be changed. Some components orcharacteristics of any embodiment may also be included in otherembodiments, or may be replaced with those of the other embodiments asnecessary. Moreover, it will be apparent that some claims referring tospecific claims may be combined with other claims referring to the otherclaims other than the specific claims to constitute the embodiment oradd new claims by means of amendment after the application is filed.

The above-mentioned embodiments of the present invention are disclosedon the basis of a data communication relationship between a userequipment and a base station. Specific operations to be conducted by thebase station in the present invention may also be conducted by an uppernode of the base station as necessary. In other words, it will beobvious to those skilled in the art that various operations for enablingthe base station to communicate with the user equipment in a networkcomposed of several network nodes including the base station will beconducted by the base station or other network nodes other than the basestation. The tem “Base Station” may be replaced with the terms fixedstation, Node-B, eNode-B (eNB), or access point as necessary. The term“terminal” may also be replaced with the term User Equipment (UE),subscriber station (SS) or mobile subscriber station (MSS) as necessary.

The embodiments of the present invention can be implemented by a varietyof means, for example, hardware, firmware, software, or a combinationthereof. In the case of implementing the present invention by hardware,the present invention can be implemented through application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in avariety of formats, for example, modules, procedures, functions, etc.Software code may be stored in a memory unit so as to be executed by aprocessor. The memory unit may be located inside or outside of theprocessor, so that it can communicate with the aforementioned processorvia a variety of well-known parts. It will be apparent to those skilledin the art that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

The present invention is applicable to a wireless communicationapparatus such as a UE, a relay and a base station.

What is claimed is:
 1. A method for managing cell status at a userequipment (UE) in a wireless communication system, the methodcomprising: configuring a first cell group having a primary cell(PCell); configuring a second cell group having one or more secondarycells (SCells); and receiving a medium access control (MAC) commandincluding a list for cell activation/deactivation, wherein, if the firstcell group and the second cell group are managed by a same base station,the list for cell activation/deactivation is associated with both of thefirst cell group and the second cell group, and wherein, if the firstcell group and the second cell group are managed by different basestations, the list for cell activation/deactivation is associated withonly one of the first cell group or the second cell group.
 2. The methodof claim 1, wherein if the first cell group and the second cell groupare managed by the different base stations, the list for cellactivation/deactivation is associated only with a corresponding cellgroup.
 3. The method of claim 1, wherein if the first cell group and thesecond cell group are managed by the different base stations, radioresource control (RRC) of the UE is managed only by a BS of the firstcell group.
 4. The method of claim 1, wherein if the first cell groupand the second cell group are managed by the different base stations,mobility management of the UE is managed only by a BS of the first cellgroup.
 5. A User Equipment (UE) for managing cell status in a wirelesscommunication system, the UE comprising: a Radio Frequency (RF) unit;and a processor, wherein the processor is configured to configure afirst cell group having a primary cell (PCell), to configure a secondcell group having one or more secondary cells (SCells), and to receive amedium access control (MAC) command including a list for cellactivation/deactivation, wherein, if the first cell group and the secondcell group are managed by a same base station, the list for cellactivation/deactivation is associated with both of the first cell groupand the second cell group, and wherein, if the first cell group and thesecond cell group are managed by different base stations, the list forcell activation/deactivation is associated with only one of the firstcell group or the second cell group.
 6. The UE of claim 5, wherein ifthe first cell group and the second cell group are managed by thedifferent base stations, the list for cell activation/deactivation isassociated only with a corresponding cell group.
 7. The UE of claim 5,wherein if the first cell group and the second cell group are managed bythe different base stations, radio resource control (RRC) of the UE ismanaged only by a BS of the first cell group.
 8. The UE of claim 5,wherein if the first cell group and the second cell group are managed bythe different base stations, mobility management of the UE is managedonly by a BS of the first cell group.